Well, to the people who say, "get over it", "natural selection killed them" and "it's just the internet", these kinds of callous sentiments are actually a big sign that there is bullying present on the internet. Whether or not people should feel bad about this bullying or take it seriously, well, the point is not whether you think it's serious, the point is, the person who committed suicide thought it was serious.
When I come here on SPPF I do take a bit of personal investment in what I say to people and people say back to me. I try to be polite and generous and in return when people are rude toward me I'm actually visibly offended in real life. There was actually one day when I got in an internet fight with a member just by asking him to be polite, and he asked me if I was on medication. I in fact, was, pain medication, and several others, and I was quite sensitive about it, and I was a little hurt by the whole fiasco. On top of many other things in real life it actually put me in a bad mood that day. Course, I learned since then to separate myself.
If you combine someone who takes the internet just as seriously as real social interaction, and the mob/snowball effect of people getting together and harrassing someone, you get a real phenomenon. Especially since it's so easy to start a meme and flame online. And you have the advantage of saying it with pictures, which is even a more hurtful way of bullying.
Plus, there are worse bullies online that sincere people don't understand. The opposite of a sincere (maybe naive) person who takes personal investment in what's online is a cynical troll who takes advantage of anonymity to act cruel, thinking it's just like a game to ruin their online experience, when in the other person's reality, their innocent cruelty is actually felt quite severely. So, it may be a case of bullying, but there is some misunderstanding involved sometimes and it's hard to actually place blame/prosecute someone.